This invention relates to methods of and agents for lubricating synthetic fibers.
During the spinning process of synthetic fibers such as polyamide and polyester fibers, it is important to prevent generation of fuzz and cause occurrence of yarn breakages. Since synthetic fibers for industrial materials such as tire cords, seat belts and air bags are produced under severe conditions of high temperature and high contact pressure and are likely to generate fuzz and yarn breakages, it is particularly important with such fibers to prevent generation of fuzz and occurrence of yarn breakages. Agents for lubricating such synthetic fibers (herein referred to simply as the lubricants) are therefore required to be capable of providing sufficient lubricity even when they are undergoing a spinning process under a condition of high temperature and high contact pressure. This invention relates to lubricating agents which can respond to such a demand and also to methods of lubricating synthetic fibers.
Examples of prior art lubricant proposed for providing lubricity to synthetic fibers including when they are undergoing a spinning process include (1) polyester obtained from polyhydroxy compound and dibasic acid having its end closed with aliphatic alcohol, its alkylene oxide adduct or aliphatic carboxylic acid (Japanese Patent Publications Tokkai 3-871 and 5-339875), (2) polyoxyalkyleneglycol with average molecular weight greater than 1000 (Japanese Patent Publication Tokkai 6-158538), (3) alkylene oxide polymers of alkylamine or dialkylamine with average molecular weight 1000-20000 (Japanese Patent Publication Tokkai 6-228885), (4) metallic salt of phosphoro-dithioate such as zinc di (di n-butylphosphoro dithioate) (Japanese Patent Publication Tokkai 3-14671 and U.S. Pat. No. 5,269,950), and (5) silane compound containing mercapto group such as .gamma.-mercaptopropyl trimethoxy silane (Japanese Patent Publication Tokkai 3-241073 and U.S. Pat. No. 5,269,950). These prior art lubricants cannot provide a high level of lubricity to synthetic fibers, however, and lubricity can be provided only to a very unsatisfactory level in the case of synthetic fibers as industrial materials adapted to be processed under a condition of high-temperature and high contact pressure such that the generation of fuzz and occurrence of yarn breakage cannot be adequately prevented. As hydrophilic agent for providing durability to polyolefin fibers, on the other hand, it has been known to use block copolymers obtained by ring-opening polymerization of aliphatic hydroxy compound with alkylene oxide and .epsilon.-caprolactone and having within the molecule polyether blocks comprising polyoxyalkylene units and polyester blocks comprising polyoxycaproyl units (Japanese Patent Publication Tokkai 8-226082) but lubricity cannot be provided to a sufficiently high level to synthetic fibers even if such block copolymers are used as lubricant and the generation of fuzz and occurrence of yarn breakage cannot be adequately prevented during their spinning process.